The present invention concerns a device for rapidly mooring a floating installation to a marine installation having a substantially stationary position relative to the water bottom and to which the floating installation is connected by means of a rigid arm.
The floating installation may be a ship and the marine installation a mooring buoy anchored at a predetermined distance from the shore. The marine installation can also be a tower, a "duc d'albe", an oscillating column, a caisson, a reservoir, etc. It can also be a buoy for loading and/or unloading cargo of a ship, an installation whereform are performed or controlled such operations as drilling of the sea bottom, recovering oil petroleum products, etc. The floating installation can also be a center for recovering thermal energy from the sea or a floating plant for treating and storing petroleum products.
There are already known systems for mooring ships to a structure such as a buoyant caisson, or to an oscillating column, which employ pivoting arms. Systems of this type are, for example, described in French Pat. No. 1,403,493 and in U.S. Pat. Nos. 3,354,479 and 3,908,212. In these systems, the mooring structure is surmounted by a rigid arm integral with the ship and in the extension of its stem on which it is articulated so as to accommodate pitching movements. To permit rotation of the arm and of the ship about the vertical axis of the mooring structure, the connection of the arm to this structure is accomplished by means of a pivot provided with ball bearings or roller bearings, this pivot making up a rotary table or orientation ring.
These prior art devices present a major inconvenience in that they do not permit the rapid mooring and release of ships on rough water, by means making up part of the ship itself. In effect, the assembly between the arm integral with the ship and the marine installation employing a rotating table regularly requires provision of means for raising or lifting exterior to the ship, which are very awkward and burdensome, and the precise positioning required can only be accomplished on a calm water surface. Generally, this assembly is effected in a shipyard on the plane of a flat water surface and the assembly formed by the buoy, the arm and the ship are towed just to the site where the system is used to proceed with the anchoring. The anchoring procedures of such an assembly are very delicate, requiring the coordination of a plurality of tows and service boats and should be effected during a meterological "window" of significant size. On the other hand, the use of the device in accordance with the invention, which makes possible a rapid mooring on the ocean of a ship to the buoy or to the oscillating column permits the accomplishment of the putting in place of the installation in two phases: the first being a classical operation of anchoring the buoy or putting in place the oscillating column, the second is a rapid operation of attaching the ship to the buoy or the oscillating column already anchored.
The use of the device in accordance with the invention likewise permits the rapid decoupling between the ship and buoy leaving the latter in place, without deterioration of the principal elements which make up the mooring device, as opposed to the manner of the device in accordance with French Pat. No. 2,442,759, wherein the rapid decoupling results in the destruction of the straps thereof. This possibility offered by the present invention is new with respect to the presently known devices and is of great interest for use with floating installations which are moored to marine installations, especially those dedicated to the exploitation of underwater petroleum, from the regions of the world wherein the ocean is relatively calm throughout the entire year (the Gulf of Mexico, Indonesia), but where there occurs from time to time a severely extreme perturbation (a hurricane, for example). Such occasional perturbations exert on these installations which should rest in place, as is the case with the present technique, forces without equal when measured against those forces which result from the regular oceanic conditions. It is desirable in this case to momentarily interrupt the exploitation and to free the ship and to leave only the bouy at the site, said bouy representing in general a mass 100 times smaller than that of the ship. It is also extremely desirable for repair work on the alone to be performed at a shipyard on the ship instead of restoring to be able to set out only one naval slip way, before restoring the ship assembly, arm and buoy on the slip way, after having released the anchoring lines and the ties to the bottom.
Finally, the present invention, contrary to the device according to French Pat. No. 2,394,443, avoids utilization of connecting lines which serve to guide the ship for effecting the mooring.